This invention relates generally to rotational actuators and, more particularly, to a rotational actuator that rotates an object in a worm-like manner.
Inchworm linear motors are piezoelectromechanical actuators that drive objects in a worm-like manner. An example of an inchworm motor is shown in FIG. 1. The driver or motor 10 typically includes three piezoelectric driver sections referred to as the forward section 12, center section 14, and rear section 16 with respect to the desired direction of movement of a linear member 20 about which the driver 10 is arranged.
In operation, a voltage is applied to the forward section 12, causing it to clamp the linear member 20 with a pair of grip members 22 attached to opposite ends of the forward section 12. A variable rate staircase voltage is applied to the center section 14 causing it to expand. The rear section 16 is attached to a housing or a stationary member. Thus, the expansion of the center section 14 drives the forward section 12 and the linear member 20 in a forward direction. A voltage is then applied to the rear section 16, causing it to clamp the linear member 20 with a pair of grip members 24 attached to opposite ends of the rear section 16. The voltage on the forward section 12 is subsequently removed, loosening the grip of the forward section 12 on the linear member 20. The staircase voltage on the center section 14, its upper limit having been reached prior to or substantially simultaneously with the application of the voltage to the rear section 16, then starts downward towards its lower limit, causing the center section 14 to contract to its original length. After the center section 14 has contracted, a voltage is then applied to the forward section 12, causing it to clamp the linear member 20, and the sequence of steps outlined above are repeated to move the linear member 20 forward in a worm-like manner.
Embodiments of the present invention are directed to rotational actuators or. rotators that move in a worm-like manner in rotation. A rotator includes piezoelectric members that are controlled to expand and contract in a predetermined sequence to rotate one object relative to another object such as a stationary support.
In accordance with an aspect of the present invention, a rotator for rotating a ring comprises a first coupling member which is adjustable in length to move between a coupled position and a decoupled position. The first coupling member has top and bottom coupling ends being coupled with the ring in the coupled position and being decoupled from the ring in the decoupled position. The rotator further comprises a second coupling member which is adjustable in length to move between a coupled position and a decoupled position. The second coupling member has top and bottom coupling ends being coupled with the ring in the coupled position and being decoupled from the ring in the decoupled position. A top advancing member is connected between the top coupling end of the first coupling member and the top coupling end of the second coupling member. The top advancing member is adjustable in length to move one top coupling end with respect to the other top coupling end. A bottom advancing member is connected between the bottom coupling end of the first coupling member and the bottom coupling end of the second coupling member. The bottom advancing member is adjustable in length to move one bottom coupling end with respect to the other bottom coupling end.
In some embodiments, the coupling members and advancing members are piezoelectric. A controller controls electrical voltages supplied to each of the coupling members and advancing members to adjust the lengths of the coupling members and advancing members. The coupling members may be attached to a stationary support.
In accordance with another aspect of the invention, a rotator for rotating a ring comprises a first piezoelectric coupling member which is adjustable in length to move between a coupled position and a decoupled position. The first coupling member has top and bottom coupling ends pressing against an inner surface of the ring in the coupled position and being spaced from the inner surface of the ring in the decoupled position. The rotator further comprises a second piezoelectric coupling member which is adjustable in length to move between a coupled position and a decoupled position. The second coupling member has top and bottom coupling ends pressing against the inner surface of the ring in the coupled position and being spaced from the inner surface of the ring in the decoupled position. A mechanism is coupled with the first and second piezoelectric coupling members for moving one piezoelectric member with respect to the other piezoelectric member in rotation with respect to the ring.
In accordance with another aspect of the present invention, a method of rotating an object comprises:
(a) coupling a first coupling member to the object and decoupling a second coupling member from the object, the first coupling member including a top coupling end and a bottom coupling end, the second coupling member including a top coupling end connected with the top coupling end of the first coupling member by a top advancing member, and a bottom coupling end connected with the bottom coupling end of the first coupling member by a bottom advancing member;
(b) adjusting a length of at least one of the advancing members to-move the second coupling member relative to the first coupling member in rotation with respect to the object;
(c) coupling the second coupling member to the object and decoupling the first coupling member from the object; and
(d) adjusting the length of at least one of the advancing members to move the first coupling member relative to the second coupling member in rotation with respect to the object.
In some embodiments, the lengths of the top and bottom advancing members are increased in (b) to move the second coupling member relative to the first coupling member in rotation with respect to the object. The lengths of the top and bottom advancing members are decreased in (d) to move the first coupling member relative to the second coupling member in rotation with respect to the object.